Field of the Invention
The present invention is directed to a shoulder implant assembly and, more specifically, to a multi-component implant assembly including a pair of receivers mounted to first and second shoulder joint defining bones. An intermediated positioned and pseudo-spherical (defined as substantially spherical with a flattened base) shaped intermediate component engages a first of the bone mounted receivers in an articulating relationship and further engages a second of the bone mounted receivers in a rotation relationship, thereby providing evenly distributed wear profiles for increased useful life of the implant, as well as relieving associated ligament tension.
Description of the Background Art
The prior art discloses various types of artificial implants, such as replacing damaged natural joint constructions including those for the shoulder. Examples of these include each of the modular humeral head resurfacing system of Winslow et al., US 2006/0009852 and US 2005/0107882, each of which incorporates a two piece humeral component for use in joint arthroplasty which is adapted to be implanted into a joint and engaged by a likewise implanted socket component.
U.S. Pat. No. 6,942,699, to Stone et al., teaches a modular shoulder prosthesis having an adjustable radial offset and/or angular inclination provided by relative rotation of an adapter interdisposed between a stem and a head. Specifically, the interface configuration between the stem and the adapter, as well as between the adapter and the head are designed such that relative positioning of these components provides a continuous adjustment in the radial offset and/or angular inclination. Indicia are provided at the interface between the adapter and the head to precisely determine the magnitude and direction of the adjustment being made.
U.S. Pat. No. 6,818,019, to Horber, teaches a joint prosthesis with a head cap connected via a collar piece to a shaft piece which may be anchored in the bone. The collar piece is coupled to the shaft piece by a joint head in a ball-jointed manner. The articulation surfaces between the joint cavity in the shaft piece and the articulation head on the collar piece are embodied such that on pressing the articulation head to the base of the joint cavity, edges or projections on the one articulation surface digs into the other articulation surface lying on a virtual spherical surface. A ball-joint like articulation is provided, whereby the spherical surfaces may have a relatively large production tolerance without the above affecting the clamping connection between the articulation surfaces.
Finally, U.S. Pat. No. 3,916,451 to Buechel et al. teaches prosthetic joints of the type used to replace dysfunctional natural joints such as the shoulder, hip, and knee. Provision of an intermediate floating bearing element to which are rotatably engaged members which are in turn secured to the appropriate bone structures results in enhanced relative motion and improved resistance to dislocation. A flange or “skirt” on the floating bearing element provides additional strength and improved function. The invention is suited to embodiments in both ball and socket and hinge type joints. Assembly and disassembly of the joint are facilitated by two-piece construction of the floating bearing element and the use of snap rings for attaching fixed bearing elements to components which may be permanently secured to the bone structure. The snap rings may be designed to support normal loads yet fracture without damage to the other components, where necessary to disassemble an implanted prosthetic joint.